It is the objective of this project to determine the number of active sites on dopamine-beta-hydroxylase, a copper protein from bovine adrenal medulla. This information will be obtained through a determination of the redox potential of dopamine-beta-hydroxylase and by determining the number of electrons transferred as a unit through potentiometric titrations. Electron paramagnetic resonance will be used to monitor the oxidation state of copper present in the enzyme.